Leukopenia is a reduction in the circulating White Blood Cells (WBC) and is often defined as WBC count to <4000/mL. The main cells involved in leukopenia are neutrophils. However a reduced number of lymphocytes, monocytes, eosinophils, or basophils may also contribute to the decreased total cell count (Merck Manual, 17th edition).
Neutropenia is characterized by a reduction in the blood neutrophil count, often leading to increased susceptibility to bacterial and fungal infections. Neutropenia is classified by the neutrophil count and the relative risk of infection: mild (1000 to 1500/mL), moderate (grade 3, 500 to 1000/mL), or severe (grade 4, <500/mL). Acute and severe neutropenia is a life-threatening condition as it predisposes the patient to rapidly fatal infections (Merck Manual, 17th edition).
Neutropenia can be caused by impaired production of neutrophils in the bone marrow, or by accelerated destruction of neutrophils. Acute neutropenia may occur over a few days when neutrophil use is rapid and production is severely impaired. Chronic neutropenia may last for many months and is often caused by reduced production or sequestration of neutrophils in the spleen. Neutropenia may be classified by whether it arises secondary to factors extrinsic to marrow myeloid cells or whether an intrinsic defect appears to be present in the myeloid progenitors (Merck Manual, 17th edition).
Neutropenia and its infectious complications are among the most common and serious adverse effects of cytotoxic chemotherapy and other cancer therapies such as radiation therapy, biotherapy, and bone marrow transplantation. Cytotoxic chemotherapy, which works by seeking out and destroying fast-growing cells, induces neutropenia because of the high proliferative rate of neutrophil precursors and the rapid turnover of blood neutrophils (Merck Manual, 17th edition). The most common symptoms of neutropenia in patients with undergoing chemotherapy include fever, mouth sores, and ear infections. Patients with profound neutropenia often suffer from pyogenic infections such as septicemia, cutaneous cellulitis, liver abscesses, furunculosis, pneumonia, stomatitis, gingivitis, perirectal inflammation, colitis, sinusitis, and otitis media. Chemotherapy may have to be delayed until the body can produce more neutrophils and a lower dosage may have to be given, resulting in the treatment being less effective.